Final answer:
Jurassic dinosaurs were not smaller than Cretaceous dinosaurs.
Step-by-step explanation:
The statement that Jurassic dinosaurs were smaller than Cretaceous dinosaurs is false. During the Cretaceous Period, dinosaurs reached their peak in size and distribution, with dinosaurs like Tyrannosaurus rex weighing at least 7 tons. The end of the Cretaceous period also marked the dramatic extinction of dinosaurs. While the Jurassic period is often associated with the first appearance of many iconic dinosaurs, it is not known for having the largest dinosaurs.